I alternate between different cable inputs on my digital front end. One cable is an Audio Alchemy powered coax.
The question: What gets "powered" in that rig?
I suspect the power was probably for the circuitry that converted Toslink to S/PDIF or for some circuitry that let you toggle between AES/EBU and S/PDIF. I can't imagine it would be for anything else, unless they were biasing the shield like the new Audioquest cables. I suppose there might've been some circuitry that "amplified" the digital signal to compensate for signal loss over reeeeally long runs. Wasn't it advertised as being good for long runs? Maybe you should write to Peter Madnick or Dusty Vawter and ask.